Last modified: 18 January 2024

Master Sources Table


Each distinct X-ray source identified on the sky is represented in the catalog by a single "master source" entry and one or more "per-stack detection" entries, one for each stack in which the source has been detected and by one or more "per-observation detection" entries, one for each observation contribution to the stack in which the source has been detected. Many of the master source properties are populated from the properties of the Best Block (the one with the largest total exposure) from the Bayesian Block Analysis (e.g., aperture photometry).

Note: Source properties in the catalog which have a value for each science energy band (type "double[6]" and "integer[6]" in the table below) have the corresponding letters appended to their names. For example, "flux_aper_b" and "flux_aper_h" represent the background-subtracted, aperture-corrected broad-band and hard-band energy fluxes, respectively.

Note: "Description" entries with a vertical bar running to the left of the text have more information available that will be displayed when the cursor hovers over the column description.

Switch to: Columns listed by Context
Column Name Type Units Description
acis_hetg_num integer total number of ACIS/HETG observations contributing to the Master Sources Table record of the source
acis_hetg_time double total livetime for all ACIS/HETG observations contributing to the Master Sources Table record of the source
acis_letg_num integer total number of ACIS/LETG observations contributing to the Master Sources Table record of the source
acis_letg_time double total livetime for all ACIS/LETG observations contributing to the Master Sources Table record of the source
acis_num integer total number of ACIS imaging observations contributing to the Master Sources Table record of the source
acis_time double total livetime for all ACIS imaging observations contributing to the Master Sources Table record of the source
apec_abund double abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_abund_hilim double abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)
apec_abund_lolim double abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
apec_abund_rhat double abundance convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_kt double keV temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_kt_hilim double keV temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)
apec_kt_lolim double keV temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
apec_kt_rhat double temperature (kT) convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_nh double HI atoms 1020 cm-2 NH column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_nh_hilim double HI atoms 1020 cm-2 NH column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)
apec_nh_lolim double HI atoms 1020 cm-2 NH column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
apec_nh_rhat double NH column density convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_norm double amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_norm_hilim double amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upperer confidence limit)
apec_norm_lolim double amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
apec_norm_rhat double amplitude convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_stat double χ2 statistic per degree of freedom of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_z double redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
apec_z_hilim double redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)
apec_z_lolim double redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
apec_z_rhat double redshift convergence criterion Redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
bb_ampl double
amplitude of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

\[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{-2} keV^{-3} s^{-1}}\right] \]
bb_ampl_hilim double
amplitude of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% upperer confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

\[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{-2} keV^{-3} s^{-1}}\right] \]
bb_ampl_lolim double
amplitude of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

\[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{-2} keV^{-3} s^{-1}}\right] \]
bb_ampl_rhat double amplitude convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum
bb_kt double keV
temperature (kT) of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

bb_kt_hilim double keV
temperature (kT) of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

bb_kt_lolim double keV
temperature (kT) of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

bb_kt_rhat double temperature (kT) convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum
bb_nh double HI atoms 1020 cm-2
NH column density of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 1020 cm-2.

bb_nh_hilim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 1020 cm-2.

bb_nh_lolim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 1020 cm-2.

bb_nh_rhat double NH column density convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum
bb_stat double
χ2 statistic per degree of freedom of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting blackbody model.

brems_kt double keV
temperature (kT) of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

brems_kt_hilim double keV
temperature (kT) of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

brems_kt_lolim double keV
temperature (kT) of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

brems_kt_rhat double temperature (kT) convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum
brems_nh double HI atoms 1020 cm-2
NH column density of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 1020 cm-2.

brems_nh_hilim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 1020 cm-2.

brems_nh_lolim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 1020 cm-2.

brems_nh_rhat double NH column density convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum
brems_norm double
amplitude of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

\[ A = \frac{3.02 \times 10^{-15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm-3 and \(D\) is the distance to the source in cm.

brems_norm_hilim double
amplitude of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% upperer confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

\[ A = \frac{3.02 \times 10^{-15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm-3 and \(D\) is the distance to the source in cm.

brems_norm_lolim double
amplitude of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

\[ A = \frac{3.02 \times 10^{-15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm-3 and \(D\) is the distance to the source in cm.

brems_norm_rhat double amplitude convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum
brems_stat double
χ2 statistic per degree of freedom of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting bremsstrahlung model.

conf_flag Boolean
source may be confused (source and/or background regions overlap in one or more contributing stacked observations)

From the Source Flags column descriptions page:

The confusion flag for a compact source is a Boolean that has a value of TRUE if the confusion code for any contributing stacked observation detection indicates that the detection's source region ellipse is confused (i.e. overlaps one of more detection source region ellipses in another stacked observation). Otherwise, the value is FALSE.

The confusion flag for an extended (convex hull) source is always NULL.

dec double deg
source position, ICRS declination

From the Position and Position Errors column descriptions page:

The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'.

dither_warning_flag Boolean
highest statistically significant peak in the power spectrum of the source region count rate occurs at the dither frequency or at a beat frequency of the dither frequency in one or more observations

From the Source Flags column descriptions page:

The dither warning flag for a compact source is a Boolean that has a value of TRUE if the dither warning flag for any contributing stacked observation detection is TRUE. Otherwise, the value is FALSE.

The dither warning flag for an extended (convex hull) source is always NULL.

err_ellipse_ang double deg
position angle (referenced from local true north) of the major axis of the 95% confidence level error ellipse

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

err_ellipse_r0 double arcseconds
major radius of the 95% confidence level position error ellipse

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

err_ellipse_r1 double arcseconds
minor radius of the 95% confidence level position error ellipse

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

extent_flag Boolean
source is extended, or deconvolved source extent is inconsistent with a point source at the 90% confidence level in one or more observations and science energy bands

From the Source Flags column descriptions page:

The extent flag for a compact source is a Boolean that has a value of TRUE if the deconvolved source extent is inconsistent with a point source at the 90% confidence level in any science energy band in any contributing observation. Otherwise, the value is FALSE.

The extent flag for an extended (convex hull) source is always TRUE.

flux_apec double ergs s-1 cm-2 net integrated 0.5-7.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum
flux_apec_aper double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_aper90 double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_aper90_hilim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_aper90_lolim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_aper_hilim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_aper_lolim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed APEC model [NH = NH(Gal); kT = 6.5 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_apec_hilim double ergs s-1 cm-2 net integrated 0.5-7.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)
flux_apec_lolim double ergs s-1 cm-2 net integrated 0.5-7.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)
flux_aper double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90 double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90_avg double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90_avg_hilim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90_avg_lolim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90_hilim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper90_lolim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper_avg double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper_avg_hilim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper_avg_lolim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper_hilim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_aper_lolim double[6] ergs s-1 cm-2
aperture-corrected net energy flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

flux_bb double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm2.

flux_bb_aper double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_aper90 double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_aper90_hilim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_aper90_lolim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_aper_hilim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_aper_lolim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed black body model [NH = NH(Gal); kT = 0.75 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_bb_hilim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm2.

flux_bb_lolim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm2.

flux_brems double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm2.

flux_brems_aper double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_aper90 double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_aper90_hilim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_aper90_lolim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_aper_hilim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_aper_lolim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed bremsstrahlung model [NH = NH(Gal); kT = 3.5 keV] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_brems_hilim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm2.

flux_brems_lolim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm2.

flux_powlaw double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm2.

flux_powlaw_aper double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_aper90 double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_aper90_hilim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_aper90_lolim double[6] ergs s-1 cm-2
PSF 90% ECF aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_aper_hilim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] (68% upper confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_aper_lolim double[6] ergs s-1 cm-2
source region aperture model energy flux inferred from the canonical absorbed power law model [NH = NH(Gal); γ = 2.0] (68% lower confidence limit) for each science energy band

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

flux_powlaw_hilim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm2.

flux_powlaw_lolim double ergs s-1 cm-2
net integrated 0.5-7.0 keV energy flux of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm2.

gal_b double deg source position, Galactic latitude (equinox J2000.0, epoch J2000.0)
gal_l double deg source position, galactic longitude (equinox J2000.0, epoch J2000.0)
hard_hm double
ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_hm_hilim double
ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio (68% upper confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_hm_lolim double
ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio (68% lower confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_hs double
ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_hs_hilim double
ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% upper confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_hs_lolim double
ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% lower confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_ms double
ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_ms_hilim double
ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% upper confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hard_ms_lolim double
ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% lower confidence limit)

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

\[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1 - H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

\[ \mathit{hard\_ms} = \frac{F(m) - F(s)}{F(m) + F(s)} \]

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

hrc_hetg_num integer total number of HRC/HETG observations contributing to the Master Sources Table record of the source
hrc_hetg_time double total livetime for all HRC/HETG observations contributing to the Master Sources Table record of the source
hrc_letg_num integer total number of HRC/LETG observations contributing to the Master Sources Table record of the source
hrc_letg_time double total livetime for all HRC/LETG observations contributing to the Master Sources Table record of the source
hrc_num integer total number of HRC imaging observations contributing to the Master Sources Table record of the source
hrc_time double total livetime for all HRC imaging observations contributing to the Master Sources Table record of the source
kp_intra_prob double[6]
intra-observation Kuiper's test variability probability (highest value across all observations); ACIS for each science energy band

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).

ks_intra_prob double[6]
intra-observation Kolmogorov-Smirnov test variability probability (highest value across all observations) for each science energy band

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).

likelihood double
highest detection log-likelihood across all stacked observations and science energy bands

From the Source Significance column descriptions page:

The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood.

The fundamental metric used to decide whether a source is included in CSC 2.0 is the likelihood,

\[ \mathcal{L}=-\ln{P} \ \mathrm{,} \]

where \(P\) is the probability that an MLE fit to a point or extended source model, in a region with no source, would yield a change in fit statistic as large or larger than that observed, when compared to a fit to background only.

The likelihood is closely related to the probability, \(P_{\mathrm{Pois}}\), that a Poisson distribution with a mean background in the source aperture would produce at least the number of counts observed in the aperture. This quantity, called detect_significance, is also reported in CSC 2.0. Smoothed background maps are used to estimate mean background, and detect_significance is expressed in terms of the number of \(\sigma\), \(z\), in a zero-mean, unit standard deviation Gaussian distribution that would yield an upper integral probability \(P_{\mathrm{Gaus}}\), from \(z\) to \(\infty\), equivalent to \(P_{\mathrm{Pois}}\). That is,

\[ P_{\mathrm{Pois}} = P_{\mathrm{Gaus}} \]

where

\[ P_{\mathrm{Gaus}} = \int_{z}^{\infty} \frac{e^{-x^{2}/2}}{\sqrt{2\pi}} dx \]
likelihood_class string highest detection likelihood classification across all stacked observations and science energy bands
major_axis double[6] arcseconds 1σ radius along the major axis of the ellipse defining the deconvolved source extent for each science energy band
major_axis_hilim double[6] arcseconds 1σ radius along the major axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band
major_axis_lolim double[6] arcseconds 1σ radius along the major axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band
man_add_flag Boolean
source was manually added in the catalog via human review

From the Source Flags column descriptions page:

The manual source addition flag for a compact source is a Boolean that has a value of TRUE if all of the stacked observation detections that contribute to the master source were manually added to the catalog by human review, i.e., man_add_flag is TRUE for all such detections. Otherwise, the value is FALSE.

The manual source addition flag for an extended (convex hull) source is set to TRUE if any of the stacked observation detections that contribute to the master source were manually added to the catalog by human review. Otherwise, the value is FALSE.

man_inc_flag Boolean
source was manually included in the catalog via human review (detection was rejected by automated criteria)

From the Source Flags column descriptions page:

The manual source inclusion flag for a compact source is a Boolean that has a value of TRUE if all of the stacked observation detections that contribute to the master source were manually included in the catalog by human review, i.e., man_inc_flag is TRUE for all such detections. Otherwise, the value is FALSE.

man_match_flag Boolean
source detections were manually matched between overlapping stacked observations via human review

From the Source Flags column descriptions page:

The manual match flag for a compact of extended (convex hull) source is a Boolean that has a value of TRUE if the set of stacked observation detections contributing to the master source was manually modified by human review, i.e. the observation detections were not matched, or were matched incorrectly, by the detection matching algorithm. Otherwise, the value is FALSE.

man_pos_flag Boolean
best fit source position was manually modified via human review

From the Source Flags column descriptions page:

The manual source position flag for a compact source is a Boolean that has a value of TRUE if the final source position was manually modified by human review in all of the stacked observation detections that contribute to the master source, i.e., man_pos_flag is TRUE for all such detections. Otherwise, the value is FALSE.

The manual source position flag for an extended (convex hull) source is set to TRUE if the final source position was manually modified by human review in any of the stacked observation detections that contribute to the master source, or if the final master source position was manually modified from the flux-weighted centroid position by human review.

man_reg_flag Boolean
source region parameters (dimensions, initial guess position input to the Maximum Likelihood Estimator fit) were manually modified via human review

From the Source Flags column descriptions page:

The manual source region parameters flag for a compact source is a Boolean that has a value of TRUE if the source region parameters were manually modified by human review in all of the stacked observation detections that contribute to the master source, i.e., man_reg_flag is TRUE for all of the contributing stacked observation detections. Otherwise, the value is FALSE.

The manual source inclusion flag for an extended (convex hull) source is set to TRUE if the source region parameters were manually modified by human review in any of the stacked observation detections that contribute to the master source, or if the source region parameters for the master extended (convex hull) source was manually modified by human review. Otherwise, the value is FALSE.

minor_axis double[6] arcseconds 1σ radius along the minor axis of the ellipse defining the deconvolved source extent for each science energy band
minor_axis_hilim double[6] arcseconds 1σ radius along the minor axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band
minor_axis_lolim double[6] arcseconds 1σ radius along the minor axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band
name string source name in the form "2CXO Jhhmmss.s{+|-}ddmmss"
nh_gal double HI atoms 1020 cm-2 Galactic NH column density in direction of source
phot_nsrcs long number of sources simultaneously fit to compute aperture photometry quantitites
photflux_aper double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90 double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90_avg double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90_avg_hilim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90_avg_lolim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90_hilim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper90_lolim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the PSF 90% ECF aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper_avg double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper_avg_hilim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper_avg_lolim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, averaged over all contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper_hilim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% upper confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

photflux_aper_lolim double[6] photons s-1 cm-2
aperture-corrected net photon flux inferred from the source region aperture, best estimate derived from the longest block of a multi-band, flux-ordered Bayesian Block analysis of the contributing observations, and calculated by counting X-ray events (68% lower confidence limit) for each science energy band

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s-1 cm-2 to ergs s-1 cm-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

pileup_flag Boolean
ACIS pile-up fraction exceeds ~10% in all observations; source properties may be affected

From the Source Flags column descriptions page:

The pileup warning flag for a compact source is a Boolean that has a value of TRUE if the pileup fraction exceeds ~10% for all contributing ACIS stacked observation detections and energy bands, i.e., pileup_flag is TRUE for all such detections. Otherwise, the value is FALSE.

The pileup warning flag for an extended (convex hull) source is always NULL.

pos_angle double[6] deg position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent for each science energy band
pos_angle_hilim double[6] deg position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band
pos_angle_lolim double[6] deg position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band
powlaw_ampl double
amplitude of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm2/keV defined at 1 keV.

powlaw_ampl_hilim double
amplitude of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm2/keV defined at 1 keV.

powlaw_ampl_lolim double
amplitude of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm2/keV defined at 1 keV.

powlaw_ampl_rhat double amplitude convergence criterion of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum
powlaw_gamma double
photon index, defined as FE ∝ E, of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

\[ F_{E} \propto E^{-\gamma} \]
powlaw_gamma_hilim double
photon index, defined as FE ∝ E, of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

\[ F_{E} \propto E^{-\gamma} \]
powlaw_gamma_lolim double
photon index, defined as FE ∝ E, of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

\[ F_{E} \propto E^{-\gamma} \]
powlaw_gamma_rhat double photon index convergence criterion of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum
powlaw_nh double HI atoms 1020 cm-2
NH column density of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 1020 cm-2.

powlaw_nh_hilim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% upper confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 1020 cm-2.

powlaw_nh_lolim double HI atoms 1020 cm-2
NH column density of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum (68% lower confidence limit)

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 1020 cm-2.

powlaw_nh_rhat double NH column density convergence criterion of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum
powlaw_stat double
χ2 statistic per degree of freedom of the best fitting absorbed power-law model spectrum to the source region aperture PI spectrum

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, and bremsstrahlung models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model spectral fit statistic is defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting absorbed power law model.

ra double deg
source position, ICRS right ascension

From the Position and Position Errors column descriptions page:

The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'.

sat_src_flag Boolean
source is saturated in all observations; source properties are unreliable

From the Source Flags column descriptions page:

The saturated source flag is for a compact source is a Boolean that has a value of TRUE if all contributing observations are ACIS observations and all stacked observation detections are significantly piled-up, i.e., sat_src_flag is TRUE for all of the contributing stacked observation detections. Source properties (including the pileup warning flag) are unreliable for all ACIS energy bands. Otherwise, the value is FALSE.

sat_src_flag for an extended (convex hull) source is always NULL.

significance double
highest flux significance across all stacked observations and science energy bands

From the Source Significance column descriptions page:

The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood.

Flux significance is a simple estimate of the ratio of the flux measurement to its average error. The mode of the marginalized probability distribution for photflux_aper is used as the flux measurement and the average error, \(\sigma_{e}\), is defined to be:

\[ \sigma_{e} = \frac{\mathit{photflux\_aper\_hilim} - \mathit{photflux\_aper\_lolim}}{2} \]

which are both used to estimate flux significance.

src_area double[6] sq. arcseconds area of the deconvolved source extent ellipse, or area of the source polygon for extended sources for each science energy band
streak_src_flag Boolean
source is located on an ACIS readout streak in all observations; source properties may be affected

From the Source Flags column descriptions page:

The streak source flag for a compact detection is a Boolean that has a value of TRUE if all of the contributing observations are ACIS observations and all stacked observation detection source regions overlap a defined region enclosing an identified readout streak, i.e. streak_src_flag is TRUE for all of the contributing stacked observation detections. Otherwise, the value is FALSE.

The streak source flag for an extended (convex hull) is TRUE if any contributing observations are ACIS observations and any stacked observation detection source region overlaps a defined region enclosing an identified readout streak. Otherwise, the value is FALSE.

var_flag Boolean
source displays flux variability within one or more observations, or between observations, in one or more energy bands

From the Source Flags column descriptions page:

The variability flag for a compact source is a Boolean that has a value of TRUE if variability is detected within any single observation in any science energy band in any of the observations contributing to the master source. Otherwise, the value is FALSE. The variability flag refers to intra-observation variability only (i.e., variability within a given observation), and its value is decided based on the variability code (var_code).

The variability flag for an extended (convex hull) source is always NULL.

var_inter_hard_flag Boolean
source hardness ratios are statistically inconsistent between two or more observations

From the Source Flags column descriptions page:

The inter-observation variable hardness ratio flag for a compact source is a Boolean that has a value of TRUE if one or more of the hardness ratios computed for any of the contributing observation detections is statistically inconsistent with the corresponding hardness ratios computed for any other contributing observation detections. Otherwise, the value is FALSE.

The inter-observation variable hardness ratio flag for an extended (convex hull) source is always NULL.

From the Source Variability column descriptions page:

A Boolean set to FALSE if var_inter_hard_prob is below 0.3 for all three hardness ratios, and set to TRUE otherwise.

var_inter_hard_prob_hm double
inter-observation ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio variability probability

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

var_inter_hard_prob_hs double
inter-observation ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability probability

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

var_inter_hard_prob_ms double
inter-observation ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability probability

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

var_inter_hard_sigma_hm double
inter-observation ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio variability standard deviation

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

\[ \left| hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}} - hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right| \]

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

var_inter_hard_sigma_hs double
inter-observation ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability standard deviation

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

\[ \left| hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}} - hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right| \]

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

var_inter_hard_sigma_ms double
inter-observation ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability standard deviation

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

\[ \left| hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}} - hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right| \]

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

var_inter_index integer[6]
inter-observation variability index in the range [0, 10]: indicates whether the source region photon flux is constant between observations for each science energy band

From the Source Variability column descriptions page:

The inter-observation variability index (var_inter_index) is an integer value in the range \([0,8]\) that is derived according to the estimated value of the quantity \(D/(N-1)\) defined above. It is used to evaluate whether the source region photon flux is constant between the observations. The degree of confidence in variability expressed by this index is similar to that of the intra-observation variability index. Below we tabulate the association between the value of \(D/(N-1)\) and inter-observation variability index.

Variability Index \(\frac{D}{N-1}\)
2 observations >2 observations
0 < 0.4 < 0.8
3 ≥ 0.4 < 0.7 ≥ 0.8 < 1.0
4 ≥ 0.7 < 1.0 ≥ 1.0 < 1.15
5 ≥ 1.0 < 2.7 ≥ 1.15 < 2.1
6 ≥ 2.7 < 7.0 ≥ 2.1 < 3.8
7 ≥ 7.0 < 12.0 ≥ 3.8 < 5.5
8 ≥ 12.0 ≥ 5.5
var_inter_prob double[6]
inter-observation variability probability, calculated from the chi^2 distribution of the photon fluxes of the individual observations for each science energy band

From the Source Variability column descriptions page:

The inter-observation variability probability (var_inter_prob) is a value that records the probability that the source region photon flux varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. Given the \(N\) individual Bayesian probability distribution of the aperture fluxes for the same source in \(N\) different observations (their means and standard deviations), we estimate for each band the maximum likelihood \(\mathcal{L}_{1}^{\mathrm{max}}\) and the corresponding maximizing arguments \(F_{\left\langle band \right\rangle}^{i,\mathrm{max}}\), of the observed fluxes assuming a different flux for each observation, as well as the maximum likelihood \(\mathcal{L}_{2}^{\mathrm{max}}\) and the corresponding maximizing argument \(F_{\left\langle band \right\rangle}^{\mathrm{max}}\) of the observed fluxes assuming a single flux (the latter is the null hypothesis of no variability). As per Wilks' theorem, the quantity:

\[ D \equiv 2 \left( \log{\mathcal{L}_{1}^{\mathrm{max}}} - \log{\mathcal{L}_{2}^{\mathrm{max}}} \right) \]

follows \(\chi^{2}\) distribution with \(N-1\) degrees of freedom, under the null hypothesis. Therefore, the null hypothesis (non-variability) is rejected with a probability proportional to the cumulative distribution of the \(\chi^{2}\) statistic for values smaller than the estimated \(D\). The quantity var_inter_prob represents this cumulative probability, and therefore gives the probability that the source is variable.

The reason for this careful definition is that the probabilities for intra-observation and inter-observation variability are, by necessity, of a different nature. Whereas one can say with reasonable certainty whether a source was variable during an observation covering a contiguous time interval, when comparing measured fluxes from different observations one knows nothing about the source's behavior during the intervening interval(s). Consequently, when the inter-observation variability probability is high (e.g., var_inter_prob > 0.7), one can confidently state that the source is variable on longer time scales, but when the probability is low, all one can say is that the observations are consistent with a constant flux.

var_inter_sigma double[6] photons s-1 cm-2
inter-observation flux variability standard deviation; the spread of the individual observation photon fluxes about the error weighted mean for each science energy band

From the Source Variability column descriptions page:

The inter-observation flux variability (var_inter_sigma) is the absolute value of the difference between the error weighted mean of the source region photon flux density PDF when a single flux is assumed \(\left( F_{\left\langle band \right\rangle}^{\mathrm{max}} \right)\), and the mean of the source region photon flux density PDF for the individual observation that maximizes the absolute value of the difference \(\left( F_{\left\langle band \right\rangle}^{i,\mathrm{max}} \right)\):

\[ \left| F_{\left\langle band \right\rangle}^{\mathrm{max}} - F_{\left\langle band \right\rangle}^{i,\mathrm{max}} \right| \]

Of all the contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation fluxes.

var_intra_index integer[6]
intra-observation Gregory-Loredo variability index in the range [0, 10]: indicates whether the source region photon flux is constant within an observation (highest value across all observations) for each science energy band

From the Source Variability column descriptions page:

The intra-observation variability index (var_intra_index) represents the highest value of the variability indices (var_index) calculated for each of the contributing observations.

var_intra_prob double[6]
intra-observation Gregory-Loredo variability probability (highest value across all observations) for each science energy band

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).